Pádraig Brady
2009-Nov-23 15:47 UTC
Re: A file cloned with "cp --reflink" different from the original one?
Jian Lin wrote:> 2009/11/23 Pádraig Brady <P@draigbrady.com>: >> Jian Lin wrote: >>> I installed BtrFS 0.19 and GNU coreutils 8.1 on my Ubuntu 9.10. >>> I tried to clone some files with "cp --reflink" to make them "copy-on-write". >>> However, I found some of the files cloned have different MD5s to the >>> original one. >>> >>> Is BtrFS (or cp with reflink) buggy? >>> Or it is indeed a feature that I used incorrectly? >>> >>> Thanks! >>> >>> root@lj-laptop:/mnt# uname -a >>> Linux lj-laptop 2.6.31-15-generic #50-Ubuntu SMP Tue Nov 10 14:54:29 >>> UTC 2009 i686 GNU/Linux >>> >>> root@lj-laptop:/mnt# mount | grep btrfs >>> /dev/sda4 on /mnt type btrfs (rw) >>> >>> root@lj-laptop:/mnt# cp --version >>> cp (GNU coreutils) 8.1 >>> >>> root@lj-laptop:/mnt# cd WinXP_CHS/ >>> root@lj-laptop:/mnt/WinXP_CHS# cp WinXP_CHS.vmdk WinXP_CHS-ref.vmdk --reflink >>> >>> root@lj-laptop:/mnt/WinXP_CHS# ls -la WinXP_CHS.vmdk WinXP_CHS-ref.vmdk >>> -rwxr-xr-x 1 root root 1713766400 Nov 23 15:11 WinXP_CHS-ref.vmdk >>> -rwxr-xr-x 1 root root 1713766400 Nov 23 13:32 WinXP_CHS.vmdk >>> >>> root@lj-laptop:/mnt/WinXP_CHS# md5sum WinXP_CHS.vmdk WinXP_CHS-ref.vmdk >>> f6da592d056167a44b089d70fa46f863 WinXP_CHS.vmdk >>> e3ee0c2c17771811c80eed088c20987d WinXP_CHS-ref.vmdk >> Yikes. Are you 100% sure nothing is changing those vm files? > > I think so. I run md5sum immediately after cloning the file. > >> Note I wouldn''t 100% trust the mtime, so an md5sum before >> and after would be good to confirm. >> >> You could try this simple prog to do the clones to >> implicate coreutils or otherwise: >> >> #include <sys/ioctl.h> >> #include <sys/types.h> >> #include <sys/stat.h> >> #include <fcntl.h> >> #include <stdio.h> >> #define BTRFS_IOC_CLONE 1074041865 >> >> int main(int argc, const char **argv) >> { >> int in = open(argv[1], O_RDONLY); >> int out = open(argv[2], O_CREAT|O_TRUNC|O_WRONLY, 0644); >> if (ioctl(out, BTRFS_IOC_CLONE, in)==-1) { >> fprintf(stderr, "ioctl error = %m\n"); >> } >> close(in); >> close(out); >> return 0; >> } > > I compiled and tried this program. > ./clone WinXP_CHS.vmdk WinXP_CHS-clone.vmdk > then I got md5 of WinXP_CHS-clone.vmdk, which is the same as that of > WinXP_CHS-ref.vmdk (made by cp --reflink), and different from the md5 > of original WinXP_CHS.vmdk. > > The cloned vm cannot run correctly, which said "hal.dll lost". The > cloned Linux vm I mentioned before also reported "/bin/bash lost". > Another tiny linux vm I cloned with the same md5 to its original vmdk > can run correctly.OK then it sounds like an issue with BTRFS (CC''d) (which could already be fixed since it''s in active development). cheers, Pádraig.
Jian Lin
2009-Nov-23 15:50 UTC
Re: A file cloned with "cp --reflink" different from the original one?
Thanks. I will try the new version soon. 2009/11/23 Pádraig Brady <P@draigbrady.com>:> Jian Lin wrote: >> 2009/11/23 Pádraig Brady <P@draigbrady.com>: >>> Jian Lin wrote: >>>> I installed BtrFS 0.19 and GNU coreutils 8.1 on my Ubuntu 9.10. >>>> I tried to clone some files with "cp --reflink" to make them "copy-on-write". >>>> However, I found some of the files cloned have different MD5s to the >>>> original one. >>>> >>>> Is BtrFS (or cp with reflink) buggy? >>>> Or it is indeed a feature that I used incorrectly? >>>> >>>> Thanks! >>>> >>>> root@lj-laptop:/mnt# uname -a >>>> Linux lj-laptop 2.6.31-15-generic #50-Ubuntu SMP Tue Nov 10 14:54:29 >>>> UTC 2009 i686 GNU/Linux >>>> >>>> root@lj-laptop:/mnt# mount | grep btrfs >>>> /dev/sda4 on /mnt type btrfs (rw) >>>> >>>> root@lj-laptop:/mnt# cp --version >>>> cp (GNU coreutils) 8.1 >>>> >>>> root@lj-laptop:/mnt# cd WinXP_CHS/ >>>> root@lj-laptop:/mnt/WinXP_CHS# cp WinXP_CHS.vmdk WinXP_CHS-ref.vmdk --reflink >>>> >>>> root@lj-laptop:/mnt/WinXP_CHS# ls -la WinXP_CHS.vmdk WinXP_CHS-ref.vmdk >>>> -rwxr-xr-x 1 root root 1713766400 Nov 23 15:11 WinXP_CHS-ref.vmdk >>>> -rwxr-xr-x 1 root root 1713766400 Nov 23 13:32 WinXP_CHS.vmdk >>>> >>>> root@lj-laptop:/mnt/WinXP_CHS# md5sum WinXP_CHS.vmdk WinXP_CHS-ref.vmdk >>>> f6da592d056167a44b089d70fa46f863 WinXP_CHS.vmdk >>>> e3ee0c2c17771811c80eed088c20987d WinXP_CHS-ref.vmdk >>> Yikes. Are you 100% sure nothing is changing those vm files? >> >> I think so. I run md5sum immediately after cloning the file. >> >>> Note I wouldn''t 100% trust the mtime, so an md5sum before >>> and after would be good to confirm. >>> >>> You could try this simple prog to do the clones to >>> implicate coreutils or otherwise: >>> >>> #include <sys/ioctl.h> >>> #include <sys/types.h> >>> #include <sys/stat.h> >>> #include <fcntl.h> >>> #include <stdio.h> >>> #define BTRFS_IOC_CLONE 1074041865 >>> >>> int main(int argc, const char **argv) >>> { >>> int in = open(argv[1], O_RDONLY); >>> int out = open(argv[2], O_CREAT|O_TRUNC|O_WRONLY, 0644); >>> if (ioctl(out, BTRFS_IOC_CLONE, in)==-1) { >>> fprintf(stderr, "ioctl error = %m\n"); >>> } >>> close(in); >>> close(out); >>> return 0; >>> } >> >> I compiled and tried this program. >> ./clone WinXP_CHS.vmdk WinXP_CHS-clone.vmdk >> then I got md5 of WinXP_CHS-clone.vmdk, which is the same as that of >> WinXP_CHS-ref.vmdk (made by cp --reflink), and different from the md5 >> of original WinXP_CHS.vmdk. >> >> The cloned vm cannot run correctly, which said "hal.dll lost". The >> cloned Linux vm I mentioned before also reported "/bin/bash lost". >> Another tiny linux vm I cloned with the same md5 to its original vmdk >> can run correctly. > > OK then it sounds like an issue with BTRFS (CC''d) > (which could already be fixed since it''s in active development). > > cheers, > Pádraig. >-- 林健 中国科学院计算技术研究所网络重点实验室 北京市海淀区科学院南路6号 邮编：100190 Jian LIN Key Laboratory of Network Science and Technology, Institute of Computing Technology, Chinese Academy of Sciences, P.O.Box 2704, Beijing 100190, China. Website: http://www.linjian.org Blog: http://blog.linjian.org E-mail/IM: lj@linjian.org -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Chris Mason
2009-Nov-23 15:52 UTC
Re: A file cloned with "cp --reflink" different from the original one?
On Mon, Nov 23, 2009 at 11:50:47PM +0800, Jian Lin wrote:> Thanks. I will try the new version soon.Note that you''ll have to reclone the files, the new version won''t fix the old clone I''m afraid. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html